This is one of the many songs that was composed by Ken Silverman, a guy who created the game called Ken's Labyrinth which looked similar to Wolfenstein 3D. It was his first game to show up commercially back in the day. Later on, Ken went to make the Build Engine which was going to be used in upcoming games such as Duke Nukem 3D, Blood, Shadow Warrior, etc. Anyway, I hope you like and enjoy the extended version of this song.
Source:
https://www.youtube.com/watch?v=BjpuyTQTWUkUploader:
Gillian Seed スナッチャー (DUDEDAMAN321)Upload date: 2014-08-06